1. Field of the Invention
Exemplary aspects of the present invention generally relate to an image forming apparatus, and more particularly to a sheet feeder in which a drive source is installed and an image forming apparatus including the sheet feeder.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet of paper, etc.) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of an image bearing member (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet of recording media; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
These image forming apparatuses often include multiple sheet feeders disposed one above the other at the bottom of the image forming apparatus. In a case in which a drive source is provided to each of the multiple sheet feeders, drive sources for all the multiple sheet feeders need to be driven when a recording medium is fed from a bottommost sheet feeder disposed at the bottom of the multiple sheet feeders, generating large noise.
Because a low-end type image forming apparatus tends to be installed near a user, there is an increasing demand for reducing noise generated by the drive sources, and various techniques for solving such a problem have been proposed. However, in the related-art techniques, reduction of noise generated by the drive sources becomes more difficult as the number of drives sources respectively provided for the multiple sheet feeders increases.
Specifically, in the related art, grip rollers are driven by the drive sources provided for the multiple sheet feeders via multiple clutches, respectively. Consequently, in a case in which a recording medium is fed from the bottommost sheet feeder, all the drive sources and the clutches must be driven to drive the grip rollers.
To reduce the size and the production cost of the image forming apparatus, a configuration in which both a clutch and an idler gear are provided to a shaft of a sheet feed roller to transmit a drive force from a motor to the sheet feed roller via the clutch and to a manual sheet feed roller via the idler gear is possible. In other words, the single drive source and clutch are used for driving the two separate rollers. However, in a case in which the image forming apparatus includes multiple sheet feeders disposed one above the other, multiple drive sources are still necessary for the multiple sheet feeders, respectively, and thus the problem of the noise generated by the multiple drive sources still remains unsolved.